MYRTLE BEACH, S.C. - The Republican presidential contenders are campaigning their way into the first of two debates before a decisive weekend vote in South Carolina.

Hours before the candidates were to gather Monday night in Myrtle Beach, S.C., for the Fox News Channel-sponsored forum, former Utah Gov. Jon Huntsman announced he was withdrawing from the race and endorsing front-runner Mitt Romney.

Romney savored the endorsement while his four pursuers struggled to emerge as the leading conservative candidate alternative to him. That dynamic was likely to play out on the debate stage, as well.